The background description provided herein is for the purpose of generally presenting the context of the disclosure. Work of the inventors hereof, to the extent the work is described in this background section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted to be prior art against the present disclosure.
Indoor positioning can be used to locate the position of a user device within an indoor environment, such as an office building. For example, the location positioning information can include floor and room information in a multi-story building. Such indoor positioning technique can also be used in asset tracking within an indoor environment. For example, a department store clerk can use indoor positioning to help a customer track the location of a sales item.
Public indoor positioning may adopt Bluetooth low energy (BLE) devices with multiple antennas. For example, the phase difference of a received signal at different receiving antennas can be used to determine the direction of the received signal, and the position of the transmitter of the received signal may thus be derived. However, due to oscillator frequency mismatch between a BLE transmitter and a BLE receiver, carrier frequency offset (CFO) may occur when the local oscillator signal at the BLE receiver does not synchronize with the carrier signal contained in the received signal. In addition, time-varying frequency drift may also occur as a result of the oscillator frequency mismatch. Such CFO and frequency drift may influence the measurement of the phase difference of the received signal at different antennas. As a result, the indoor positioning estimation may not be accurate.